I'm not sure how the EU charter works for geographic limits, but Canada would be a phenomenal addition to the market, especially since the US is about to blow up NAFTA and other trade agreements with Canada and Mexico.
If I'm not mistaken, per article 49 of the Treaty on European Union, it can't.
Any European State which respects the values referred to in Article 2 and is committed to promoting them may apply to become a member of the Union. The European Parliament and national Parliaments shall be notified of this application. The applicant State shall address its application to the Council, which shall act unanimously after consulting the Commission and after receiving the consent of the European Parliament, which shall act by a majority of its component members. The conditions of eligibility agreed upon by the European Council shall be taken into account.
The conditions of admission and the adjustments to the Treaties on which the Union is founded, which such admission entails, shall be the subject of an agreement between the Member States and the applicant State. This agreement shall be submitted for ratification by all the contracting States in accordance with their respective constitutional requirements.
For example, Morocco tried applying, but was rejected because it wasn't considered an "European State". So, from my point of view, either EU amends the article to allow non-European countries to join (maybe on the basis of cultural similarities? anyways, I don't think it's even feasible), or an special agreement/set of agreements to integrate it in the EU without actually making it part of the EU.
I think originally it was meant to be focused on geographical Europe, they could use the "culturally European " reasoning as a loophole (or as the new meaning), though, but I don't really know.
Georgia is absolutely within Europa by geographical, historically and politically.
The eastern and southern reaches of the Caucasus mountains define the border towards Asia in that region.
What about Russia? I mean hypothetically, if they weren't being utter cunts, of course. What makes Russia Russia is entirely in Europe, but the country is so stupidly big, 2/3 of its land is still in Asia.
Similar question for Turkey. They have East Thrace in Europe, and around half of their biggest city, but almost everything that makes Turkey Turkey is in Asia. They're arguably much more Asian than Russia but somehow they'd be considered for application if their government were to become civilised.
Russia absolutely would be a candidate if it ever will fullfill the requisites - the absolute majority of the population lives on the European side of the Ural anyway.
In reality Russia always had the false "world power" idea so they never even considered it (and besides always weren't even close to fullfill any criteria).
Turkey was actually on it's way towards becoming a candidate in the early 2000 years, but there was heavy resistance from some countries (mainly the conservatives/right wings in Germany and Austria), but they were also against the Baltics, the Eastern European states, etc. Which is now totally acceptable.
It ended with Erdogan becoming what he is now. Today I see no chance that they will become a member within the next 30 years as the rules have tightened in some aspects.
Europe is not well defined, there are different opinions where Europe ends and Asia begins. Depending on the definition you choose, Georgia can be seen as partially or even completely in Europe.
On the other hand, there is not much discussion that the Atlantic is the western border of Europe, so Canada is definitely not in Europe.